| Commit message (Collapse) | Author | Age | Files | Lines |
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This enables per-object SMP locks on SMP configurations and is the first
step to support fine-grained locking. On uni-processor configuration
there will be no overhead. The _Objects_Acquire() is intended to
replace _Objects_Get_isr_disable().
Update #2273.
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Make <rtems/score/atomic.h> available for all RTEMS configurations. Use
inline functions instead of macros. Use ISR disable/enable on
uni-processor configurations to ensure atomicity.
Update #2273.
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Ensure that the global construction is performed in the context of the
first initialization thread. On SMP this was not guaranteed in the
previous implementation.
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This lays the proper structure for doing future work on
time adjustment algorithms. Any TOD adjustments should be
requested at the API level and performed at the SCORE level.
Additionally updated a test.
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There was a lot of duplication between the discipline subroutines.
With the transition to RBTrees for priority discipline, there were
only a few lines of source code manipulating the data structure
for FIFO and priority. Thus is made sense to fold these back
into the main methods.
As part of doing this all of the tests for discipline were changed
to be in the same order.
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The following scheduler operations return a thread in need for help
- unblock,
- change priority, and
- yield.
A thread in need for help is a thread that encounters a scheduler state
change from scheduled to ready or a thread that cannot be scheduled in
an unblock operation. Such a thread can ask threads which depend on
resources owned by this thread for help.
Add a new ask for help scheduler operation. This operation is used by
_Scheduler_Ask_for_help() to help threads in need for help returned by
the operations mentioned above. This operation is also used by
_Scheduler_Thread_change_resource_root() in case the root of a resource
sub-tree changes. A use case is the ownership change of a resource.
In case it is not possible to schedule a thread in need for help, then
the corresponding scheduler node will be placed into the set of ready
scheduler nodes of the scheduler instance. Once a state change from
ready to scheduled happens for this scheduler node it may be used to
schedule the thread in need for help.
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The _Scheduler_Yield() was called by the executing thread with thread
dispatching disabled and interrupts enabled. The rtems_task_suspend()
is explicitly allowed in ISRs:
http://rtems.org/onlinedocs/doc-current/share/rtems/html/c_user/Interrupt-Manager-Directives-Allowed-from-an-ISR.html#Interrupt-Manager-Directives-Allowed-from-an-ISR
Unlike the other scheduler operations the locking was performed inside
the operation. This lead to the following race condition. Suppose a
ISR suspends the executing thread right before the yield scheduler
operation. Now the executing thread is not longer in the set of ready
threads. The typical scheduler operations did not check the thread
state and will now extract the thread again and enqueue it. This
corrupted data structures.
Add _Thread_Yield() and do the scheduler yield operation with interrupts
disabled. This has a negligible effect on the interrupt latency.
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This scheduler attempts to account for needed thread migrations caused
as a side-effect of a thread state, affinity, or priority change operation.
This scheduler has its own allocate_processor handler named
_Scheduler_SMP_Allocate_processor_exact() because
_Scheduler_SMP_Allocate_processor() attempts to prevent an executing
thread from moving off its current CPU without considering affinity.
Without this, the scheduler makes all the right decisions and then
they are discarded at the end.
==Side Effects of Adding This Scheduler==
Added Thread_Control * parameter to Scheduler_SMP_Get_highest_ready type
so methods looking for the highest ready thread can filter by the processor
on which the thread blocking resides. This allows affinity to be considered.
Simple Priority SMP and Priority SMP ignore this parameter.
+ Added get_lowest_scheduled argument to _Scheduler_SMP_Enqueue_ordered().
+ Added allocate_processor argument to the following methods:
- _Scheduler_SMP_Block()
- _Scheduler_SMP_Enqueue_scheduled_ordered()
- _Scheduler_SMP_Enqueue_scheduled_ordered()
+ schedulerprioritysmpimpl.h is a new file with prototypes for methods
which were formerly static in schedulerprioritysmp.c but now need to
be public to be shared with this scheduler.
NOTE:
_Scheduler_SMP_Get_lowest_ready() appears to have a path which would
allow it to return a NULL. Previously, _Scheduler_SMP_Enqueue_ordered()
would have asserted on it. If it cannot return a NULL,
_Scheduler_SMP_Get_lowest_ready() should have an assertions.
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Replace _Per_CPU_State_wait_for_ready_to_start_multitasking() with
_Per_CPU_State_wait_for_non_initial_state(). Implement this function.
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Replace _Scheduler_Allocate() with _Scheduler_Node_initialize(). Remove
the return status and thus the node initialization must be always
successful.
Rename _Scheduler_Free() to _Scheduler_Node_destroy().
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A resource is something that has at most one owner at a time and may
have multiple rivals in case an owner is present. The owner and rivals
are impersonated via resource nodes. A resource is represented via the
resource control structure. The resource controls and nodes are
organized as trees. It is possible to detect deadlocks via such a
resource tree. The _Resource_Iterate() function can be used to iterate
through such a resource tree starting at a top node.
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Add basic support for the Multiprocessor Resource Sharing Protocol
(MrsP).
The Multiprocessor Resource Sharing Protocol (MrsP) is defined in A.
Burns and A.J. Wellings, A Schedulability Compatible Multiprocessor
Resource Sharing Protocol - MrsP, Proceedings of the 25th Euromicro
Conference on Real-Time Systems (ECRTS 2013), July 2013. It is a
generalization of the Priority Ceiling Protocol to SMP systems. Each
MrsP semaphore uses a ceiling priority per scheduler instance. These
ceiling priorities can be specified with rtems_semaphore_set_priority().
A task obtaining or owning a MrsP semaphore will execute with the
ceiling priority for its scheduler instance as specified by the MrsP
semaphore object. Tasks waiting to get ownership of a MrsP semaphore
will not relinquish the processor voluntarily. In case the owner of a
MrsP semaphore gets preempted it can ask all tasks waiting for this
semaphore to help out and temporarily borrow the right to execute on one
of their assigned processors.
The help out feature is not implemented with this patch.
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This function is only used by _Thread_Change_priority(). Make it static
to avoid the function call overhead in the performance critical function
_Thread_Change_priority().
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The function to change a thread priority was too complex. Simplify it
with a new scheduler operation. This increases the average case
performance due to the simplified logic. The interrupt disabled
critical section is a bit prolonged since now the extract, update and
enqueue steps are executed atomically. This should however not impact
the worst-case interrupt latency since at least for the Deterministic
Priority Scheduler this sequence can be carried out with a wee bit of
instructions and no loops.
Add _Scheduler_Change_priority() to replace the sequence of
- _Thread_Set_transient(),
- _Scheduler_Extract(),
- _Scheduler_Enqueue(), and
- _Scheduler_Enqueue_first().
Delete STATES_TRANSIENT, _States_Is_transient() and
_Thread_Set_transient() since this state is now superfluous.
With this change it is possible to get rid of the
SCHEDULER_SMP_NODE_IN_THE_AIR state. This considerably simplifies the
implementation of the new SMP locking protocols.
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Rename scheduler per-thread information into scheduler nodes using
Scheduler_Node as the base type. Use inheritance for specialized
schedulers.
Move the scheduler specific states from the thread control block into
the scheduler node structure.
Validate the SMP scheduler node state transitions in case RTEMS_DEBUG is
defined.
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Make rtems_task_get_affinity() and rtems_task_set_affinity() available
on non-SMP configurations. Allow larger CPU sets.
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The thread control block contains fields that point to application
configuration dependent memory areas, like the scheduler information,
the API control blocks, the user extension context table, the RTEMS
notepads and the Newlib re-entrancy support. Account for these areas in
the configuration and avoid extra workspace allocations for these areas.
This helps also to avoid heap fragementation and reduces the per thread
memory due to a reduced heap allocation overhead.
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Delete global variables _Priority_Major_bit_map and _Priority_Bit_map.
This makes it possible to use multiple priority scheduler instances for
example with clustered/partitioned scheduling on SMP.
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The thread deletion is now supported on SMP.
This change fixes the following PRs:
PR1814: SMP race condition between stack free and dispatch
PR2035: psxcancel reveals NULL pointer access in _Thread_queue_Extract()
The POSIX cleanup handler are now called in the right context (should be
called in the context of the terminating thread).
http://pubs.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_09.html
Add a user extension the reflects a thread termination event. This is
used to reclaim the Newlib reentrancy structure (may use file
operations), the POSIX cleanup handlers and the POSIX key destructors.
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Delete _Watchdog_Report_chain(). These two functions use printk() with
thread dispatching and interrupts disabled. So they are pretty useless
in real applications. They are not part of the application APIs. They
are only used in one test and do nothing useful in this test.
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Add _Debug_Is_thread_dispatching_allowed(). This makes it possible to
assert the opposite.
Use _ISR_Disable_without_giant()/_ISR_Enable_without_giant() to avoid
misleading secondary assertion failures.
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Add per-CPU profiling stats API. Implement the thread dispatch disable
level profiling. The interrupt profiling must be implemented in CPU
port specific parts (mostly assembler code). Add a support function
_Profiling_Outer_most_interrupt_entry_and_exit() for this purpose.
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This new Score Handler provides a structure to manage a
cpu_set_t plus helper routines to validate the contents
against the current system configuration.
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Rename rtems_smp_process_interrupt() into
_SMP_Inter_processor_interrupt_handler(). Delete unused header file
<rtems/bspsmp.h>.
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Collect SMP implementation specific parts in the
<rtems/score/smpimpl.h> header file.
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Tested and implemented on ARM, m68k, PowerPC and SPARC. Other
architectures need more work.
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Add Timestamp support in the score to return a timestamp in nanoseconds.
Add a test.
Update the RTEMS API documentation.
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The user of the red-black tree container must now ensure that at most
one thread at once can access an instance.
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Rename _Scheduler_simple_smp_Start_idle() to
_Scheduler_SMP_Start_idle().
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Replace Scheduler_simple_smp_Control with Scheduler_SMP_Control. Rename
_Scheduler_simple_smp_Instance() to _Scheduler_SMP_Instance().
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Delete _Priority_bit_map_Handler_initialization() and rely on BSS
initialization. Move definition of _Priority_Major_bit_map and
_Priority_Bit_map to separate file. Move definition of __log2table also
to this file.
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Add call to _Scheduler_Schedule() in missing path after
_Thread_Set_transient() in _Thread_Change_priority(). See also
sptests/spintrcritical19.
Add thread parameter to _Scheduler_Schedule(). This parameter is
currently unused but may be used in future SMP schedulers.
Do heir selection in _Scheduler_Schedule(). Use
_Scheduler_Update_heir() for this in the particular scheduler
implementation.
Add and use _Scheduler_Generic_block().
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Use a per-CPU thread dispatch disable level. So instead of one global
thread dispatch disable level we have now one instance per processor.
This is a major performance improvement for SMP. On non-SMP
configurations this may simplifiy the interrupt entry/exit code.
The giant lock is still present, but it is now decoupled from the thread
dispatching in _Thread_Dispatch(), _Thread_Handler(),
_Thread_Restart_self() and the interrupt entry/exit. Access to the
giant lock is now available via _Giant_Acquire() and _Giant_Release().
The giant lock is still implicitly acquired via
_Thread_Dispatch_decrement_disable_level().
The giant lock is only acquired for high-level operations in interrupt
handlers (e.g. release of a semaphore, sending of an event).
As a side-effect this change fixes the lost thread dispatch necessary
indication bug in _Thread_Dispatch().
A per-CPU thread dispatch disable level greatly simplifies the SMP
support for the interrupt entry/exit code since no spin locks have to be
acquired in this area. It is only necessary to get the current
processor index and use this to calculate the address of the own per-CPU
control. This reduces the interrupt latency considerably.
All elements for the interrupt entry/exit code are now part of the
Per_CPU_Control structure: thread dispatch disable level, ISR nest level
and thread dispatch necessary. Nothing else is required (except CPU
port specific stuff like on SPARC).
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Rename _Scheduler_simple_Update() in _Scheduler_default_Update().
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Rename _Scheduler_simple_Allocate() in _Scheduler_default_Allocate().
Rename _Scheduler_simple_Free() in _Scheduler_default_Free().
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Rename _Scheduler_priority_Release_job() into
_Scheduler_default_Release_job().
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